As an antenna apparatus using multiple antenna elements and selectively switching among them, for example, a diversity antenna apparatus disclosed in Patent Literature 1 has been known.
The diversity antenna apparatus of Patent Literature 1 is provided with impedance adjustment units each disposed between one of two antennas as a diversity antenna and a switching circuit. The impedance adjustment units provide an adjustment for an antenna disconnected by the switching circuit, such that the switching circuit side terminates with no reflection as seen from the antenna. Thus, high isolation between the antennas can be achieved.
As described above, according to Patent Literature 1, it is possible to provide a diversity antenna apparatus capable of suppressing re-radiation from a disconnected antenna by means of no reflection provided by a corresponding impedance adjustment unit, and thus achieving good isolation characteristics between two antennas.
Further, as a conventional antenna apparatus provided with an array antenna made of a loop antenna and a monopole antenna, there is, for example, an antenna apparatus disclosed in Patent Literature 2.
The antenna apparatus of Patent Literature 2 is provided with a diversity antenna made of a loop antenna and a monopole antenna, and thus achieves high isolation, and simultaneously achieves low correlation through different directivities and different polarizations. The high isolation between the antennas yields an improvement in radiation efficiency, and the low correlation yields a high diversity characteristic. Accordingly, a high diversity effect can be obtained.
As described above, according to Patent Literature 2, it is possible to provide an antenna apparatus with a loop antenna and a monopole antenna, capable of achieving high isolation and low correlation and thus obtaining a high diversity effect, despite the arrangement of the two antennas close to each other.